Generally, a nonisolated switching DC-DC converter is powered from a voltage source connected to an input terminal and maintains output voltages to be constant regardless of loading conditions. The nonisolated switching DC-DC converter can be classified into a voltage boosting (step-up) or voltage step-down type according to the polarity and size of the output voltage in relation to the input voltage.
The conventional DC-DC converter using one voltage source typically applies a smooth start function in which its Pulse Width Modulation (PWM) switching duty gradually varies during the initial operation, thereby avoiding the generation of an inrush current.
However, there is a drawback in DC-DC converters using two voltage sources for the input and output thereof in that when a stop mode is converted into a drive mode or during power input (i.e., the switching operation is not instantaneously executed due to duty ratios determined according to the battery voltage during reactivation), the two voltages are shorted to each other, causing an indefinite current flow and damage to elements.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement of any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.